Disposable wiper products such as paper towels, industrial wipers, and other similar products are designed to include several important properties. For example, the products should have good bulk, a soft feel and should be highly absorbent. The products should also have good strength even when wet and should resist tearing. The wiping products should also have good stretch characteristics, should be abrasion resistant, and should not deteriorate in the environment in which they are used.
In the past, many attempts have been made to enhance and increase certain physical properties of disposable wiping products. Unfortunately, however, when steps are taken to increase one property of a wiping product, other characteristics of the product may be adversely affected. For instance, in cellulosic based wiping products, softness is typically increased by decreasing or reducing cellulosic fiber bonding within the paper product. Inhibiting or reducing fiber bonding, however, adversely affects the strength of the paper web.
One particular process that has proven to be very successful in producing paper towels and other wiping products is disclosed in U.S. Pat. No. 3,879,257 to Gentile, et al., which is incorporated herein by reference in its entirety. In Gentile, et al., a process is disclosed for producing soft, absorbent, single ply fibrous webs having a laminate-like structure that are particularly well suited for use as wiping products.
The fibrous webs disclosed in Gentile, et al. are formed from an aqueous slurry of principally lignocellulosic fibers under conditions which reduce interfiber bonding. A bonding material, such as a latex elastomeric composition, is applied to a first surface of the web in a spaced-apart pattern. In particular, the bonding material is applied so that it covers from about 50% to about 60% of the surface area of the web. The bonding material provides strength to the web and abrasion resistance to the surface. Once applied, the bonding material can penetrate the web preferably from about 10% to about 40% of the thickness of the web.
The bonding material can then be similarly applied to the opposite side of the web for further providing additional strength and abrasion resistance. Once the bonding material is applied to the second side of the web, the web can be brought into contact with a creping surface. Specifically, the web will adhere to the creping surface according to the pattern to which the bonding material was applied. The web is then creped from the creping surface with a doctor blade. Creping the web greatly disrupts the fibers within the web, thereby increasing the softness, absorbency, and bulk of the web.
In one of the preferred embodiments disclosed in Gentile, et al., both sides of the paper web are creped after the bonding material has been applied. Gentile, et al. also discusses the use of chemical debonders to treat the fibers prior to forming the web in order to further reduce interfiber bonding and to increase softness and bulk.
The processes as disclosed in Gentile, et al. have provided great advancements in the art of making disposable wiping products. The products, however, tend to be somewhat expensive to produce due in part to the cost of the latex bonding material that is applied to each side of the web and due to the equipment and energy requirements needed to apply and cure the bonding material. Further, besides being one of the more expensive components of the product, in some applications, the latex bonding material when cross-linked and cured may form formaldehyde. When formaldehyde is formed, precautions must be taken to ensure that the formaldehyde does not create any health risks and is not released to the environment.
Thus, it would be desirable if disposable wiping products having properties similar to those disclosed in Gentile, et al. could be produced without using a latex bonding material. More particularly, a need exists for a method of producing wiping products having good softness, bulk, absorbency and strength that can be made without having to use a latex adhesive. A need also exists for a method of producing wiping products that will not degrade significantly when exposed to solvents and chemicals as will be described in more detail hereinafter.